The present invention relates to ammunitions for small or medium calibre firearms and in particular to ammunitions for hunting firearms or weapons.
The French patent No. 83.18988 discloses an ammunition comprising an undergauged projectile stabilized by a feathering or tail fins which is actuated by the firing of a charge of propellant powder contained in a case; the pressure of the gas resulting from such a firing acts upon the rear portion of the sabot. This type of action is similar to that encountered with hunting cartridges fitted with conventional bullets and the major drawback is that the expansion ratio c/c' (c being the total volume of the bore, the case being inserted into the barrel or tube and c' being the volume assigned to the powder, the cartridge being in its operation position) is very large and may even exceed 40 for certain loadings. Now, an expansion ratio of too great value has a consequence an initial non-optimum velocity.